Black ghost knifefish

Aquarium fish: Black ghost knifefish (Apteronotus albifrons)
Size: 30 cm
Origin: South America
Water temperature: 23-28 ° C
Aquarium volume: 350 l

Black ghost knifefish (Apteronotus albifrons ) – also known as the Brazilian Ghost, one of the most unique freshwater fish kept in aquariums that uses the sense of electroreception.


The species is native to South America . It lives in the rushing waters of the Amazon basin (Venezuela, Paraguay, Peru). In the rainy season, it migrates to flooded forest areas.

Characteristics and disposition

Under natural conditions, they reach 50 cm in length – in aquariums they do not exceed 30 cm.

The Amazon spirit has a specific structure. The body of the fish is elongated, strongly laterally flattened, tapering towards the back – it resembles the shape of a knife (hence the English name knife fish). Coloration of the body black with light discoloration on the body and caudal fin. There are also some types of albino in trade. Just behind the head is the rectum with a wavy, very long, fleshy anal fin.

Behind the gill covers are pectoral fins, the caudal fin is elongated and slightly rounded at the tip, the dorsal fin is threadlike and almost invisible. The sex of the fish is very difficult to distinguish. The shape of the male’s head may slightly resemble a horse’s head. An adult female may be slightly thicker. Amazon spirits do not have scales on their bodies and are therefore very sensitive to medicines.

Medicines should be administered in no more than half the recommended dose, with caution. These fish generate a small electric field , about 1 kHz, necessary for electron navigation and electrolocation, i.e. to move, search for food and communicate with each other. Two types of highly sensitive and specialized electroreceptors are abundantly distributed over the entire surface of the body. Some are responsible for receiving low-frequency signals generated by other organisms, the other high-frequency, they detect changes in the electric field generated by their own organs.

Nutrition and feeding

Predatory fish are not very eager to eat dry food . Their diet should mainly include live or frozen foods, e.g. insect larvae, earthworms, fish meat. Despite the night-time lifestyle, after acclimatization they go out to look for food also during the day.


They require a spacious tank of at least 350 liters , with numerous hiding places, for example made of stones, roots, branches, PVC pipes, clay pipes, etc.

They prefer poor lighting, preferably the lack of it. Highly efficient filter required. The water should be changed at least once a week with fresh water in the amount of 30-50%. A UV lamp will also be useful, as it will reduce the risk of disease. These fish like a fairly strong current of water.

Amazon spirits have a rather calm disposition, but in too small an aquarium they can be aggressive towards others and their species. Smaller fish and crustaceans will sooner or later be eaten. Species with similar sizes and environmental requirements will be a good company.


The species is very difficult to reproduce at home. Amazon spirits are bred on farms in Asia, where special hormones are used for this purpose.


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